12 Twisted pair CableThe Electronic Industries Association (EIA) has developed standards to grade UTP.Category 1. The basic twisted-pair cabling used in telephone systems. This level of quality is fine for voice but inadequate for data transmission.Category 2. This category is suitable for voice and data transmission of up to 2Mbps.Category 3.This category is suitable for data transmission of up to 10 Mbps. It is now the standard cable for most telephone systems.Category 4. This category is suitable for data transmission of up to 20 Mbps.Category 5. This category is suitable for data transmission of up to 100 Mbps.

23 Fiber Optic Cable Fiber Optic CableMetal cables transmit signals in the form of electric current.Optical fiber is made of glass or plastic and transmits signals in the form of light.Light, a form of electromagnetic energy, travels at 300,000 Kilometers/second (186,000 miles/second), in a vacuum.The speed of the light depends on the density of the medium through which it is traveling (the higher density, the slower the speed).

25 Fiber Optic Types multimode step-index fiberthe reflective walls of the fiber move the light pulses to the receivermultimode graded-index fiberacts to refract the light toward the center of the fiber by variations in the densitysingle mode fiberthe light is guided down the center of an extremely narrow core

29 Unguided mediaUnguided media, or wireless communication, transport electromagnetic waves without using a physical conductor.Instead the signals are broadcast though air or water, and thus are available to anyone who has a device capable of receiving them.The section of the electromagnetic spectrum defined as radio communication is divided into eight ranges, called bands.

30 AntennasElectrical conductor (or system of..) used to radiate electromagnetic energy or collect electromagnetic energyTransmissionRadio frequency energy from transmitterConverted to electromagnetic energyBy antennaRadiated into surrounding environmentReceptionElectromagnetic energy impinging on antennaConverted to radio frequency electrical energyFed to receiverSame antenna often used for both

31 Wireless (Unguided Media) Transmissiontransmission and reception are achieved by means of an antennadirectionaltransmitting antenna puts out focused beamtransmitter and receiver must be alignedomnidirectionalsignal spreads out in all directionscan be received by many antennas

32 Directional AntennaDirectional Antennas provide great efficiency of power transmission because the power can be focused into a narrow beam directed toward the station of interest.

33 Omnidirectional AntennaOmnidirectional Antenna is widely used for radio broadcasting antennas, in mobile devices that use radio such as cell phones, FM radios, walkie-talkies, wireless computer networks, cordless phones, GPS

34 Propagation of Radio WavesRadio technology considers the earth as surrounded by two layers of atmosphere: the troposphere and the ionosphere.The troposphere is the portion of the atmosphere extending outward approximately 30 miles from the earth's surface.The troposphere contains what we generally think of as air. Clouds, wind, temperature variations, and weather in general occur in the troposphere.The ionosphere is the layer of the atmosphere above the troposphere but below space.

36 Propagation of Radio WavesGround propagation: radio waves travel through the lowest portion of the atmosphere, hugging the earth. These low-frequency signals emanate in all directions from the transmitting antenna and follow the curvature of the planet. The distance depends on the power in the signal.In Sky propagation, higher-frequency radio waves radiate upward into the ionosphere where they are reflected back to earth. This type of transmission allows for greater distances with lower power output.In Line-of-Sight Propagation, very high frequency signals are transmitted in straight lines directly from antenna to antenna.

39 Satellite Microwave Satellite is relay stationSatellite receives on one frequency, amplifies or repeats signal and transmits on another frequencyRequires geo-stationary orbitHeight of 35,784kmTelevisionLong distance telephonePrivate business networks

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